Hi, Ben
If everything is working and operating fine, You must have changed or run some G-code that set Mach or Left Mach in a different Normal Condition/Abnormal Condition.
I don't have a list of these item's, But it can be as simple as running some G-code that leaves Mach in a G91 inc. mode,
If your Normal Condition on startup is G90 abs. mode, The button will flash green/yellow.
With the Msg you have, A g90 or g91 on the MDI line should re-set/fix it.
To reset the Normal Condition/Abnormal Condition, green/yellow flashing back to Green, Just Double-Click on the Button and say yes to the Prompt Msg.
Thanks, Chip